Challenge:How are oil and gas extracted?

Teachers’ notes

Using this challenge

Teacher slide 1

Learning outcomesSee Science at Work teachers’ notes.

PreparationPrepare the apparatus on Student slide 4 for a demo or class practical.Props: sponge or piece of foam to help illustrate porosity; bottle of sparkling mineral water or fizzy drink; balloon for differentiation activityOptional: microwave some popcorn to demonstrate how it ‘pops’

StarterUse the Discovering oil and gas case study to review where oil and gas are found. Do students think reservoirs are more like open caves or porous sponges? How does BP extract the oil and gas?

Main activityWork through the slides. Answers are provided on Teacher slides 2 and 3. Open the fizzy drink at Student slide 3. Use the popcorn with Student slides 6 and 7.

PlenaryReview how oil and gas are trapped at pressure in porous rocks. Use Student slide 8 to establish the benefits of Bright Water against the wider context of finite oil and gas reserves and increasing demand.

Differentiation – EasierStudent slide 6: Show students an empty bottle to represent a rock pore. Show that you can fit a deflated balloon (a Bright Water molecule) into the container. Inflate the balloon inside to ‘block’ the pore with the expanded ‘molecule’.

Differentiation – HarderStudent slide 4: Discuss what would happen if the bottom of the flask were porous.

Answers

Teacher slide 2

1. The rocks containing the oil are porous and permeable – both properties are essential; the rocks trapping the oil are impermeable. (Hint: Ask students to consider the structures, and how oil and gas might move through them.)

2. More rocks press down from above and the weight of these rocks increases the pressure. (Hint: Think of someone carrying a pile of books. How does it feel as more books are added?)

3. Seawater also presses down on the rocks.

4. Bubbles of trapped gas fizz from the drink because the pressure in the bottle is greater than that of the air in the room.

5. Oil initially comes out of the well by itself because the pressure inside the well is higher than outside it. As oil escapes, the pressure reduces, so the oil eventually stops escaping. (Hint: Compare how the bubbles eventually stop escaping from the bottle of fizzy drink.)

6. The water will push the oil out of the flask because the pressure in the flask will rise as water is added. Oil escapes until the pressure equalises.

7. The oil is pushed out in the same way as in the experiment. BP continues to inject water so that the pressure remains higher inside the well than outside it.

Answers

Teacher slide 3

8. Some rocks trap oil, but allow injected water to pass through their pores. The Bright Water molecules are small enough to enter the pores with the water at first. When they get hot and ‘pop’, their increased size blocks the pores so that water cannot escape. Instead, the water pushes the remaining oil out.

9. Some reservoirs are deeper underground than others, and the temperature tends to increase with depth.

10. Bright Water allows BP to extract more oil from each reservoir. This improves the economic viability of each field, as well as helping to meet ever-increasing demand for oil and gas. Remember that reserves are finite.

© BP International Ltd 2008

Challenge:How are oil and gas extracted?

Challenge presentation

What is it like underground?

Geologists look for oil and gas in special types of rock formation. One type of rock contains the oil and gas. Another stops them from escaping.

1. What are the important properties of the two types of rock?

Student slide 1

What causes pressure?

BP is developing the Prudhoe Bay oil field in Alaska. The rocks beneath the bay are under enormous pressure.

2. Why does the pressure increase as you go deeper underground?

Parts of one reservoir at Prudhoe Bay lie under the seabed.

3. Why does this increase the pressure?

Student slide 2

To be supplied

Pushing oil from the ground

4. What happens when you open a bottle of fizzy drink?

BP engineers sometimes deal with a similar effect when an oil well is ‘opened’.

5. What do you think happens:– when the oil starts to

flow from the well?– after some oil has

been extracted?

Student slide 3

Maintaining the pressure

Only 10–20% of the oil in a reservoir flows out naturally because of the pressure underground. Engineers must find ways to extract more of the oil.

6. What will happen to the oil when water is injected into the flask shown in the diagram?

Student slide 4

Using water to extract oil

BP engineers inject water into the oil reservoirs at Prudhoe Bay.

7. What will happen to the oil in the reservoir when BP injects water?

This does not always work well. Some permeable rocks allow water to escape from the reservoir.

Student slide 5

Introducing Bright Water

In Prudhoe Bay, BP engineers have added a polymer called Bright Water to the injection water.

Each molecule acts like popcorn and expands to ten times its original size when heated by the hot rock of the reservoir.

8. How could Bright Water stop water escaping through the rock?

Student slide 6

How Bright Water solves the problem

Bright Water blocks the pores in surrounding rocks so that the water can push oil out of the well.

Bright Water molecules can be altered so that they ‘pop’ at different temperatures. This means Bright Water could be used in different locations.

9. Why might some oil reservoirs be hotter than others?

Student slide 7

Why is Bright Water important?

Oil wells are very expensive to drill. Bright Water may become an important new tool that BP can use to get as much oil and gas from the ground as possible.

10. Why could Bright Water be an important new technology?

Student slide 8